Technical information

D. Error Detection Circuit
(NP2020)
The error detection circuit is found on the DC
controller PCB and serves to monitor the fixing
temperature and scanning lamp; Le., abnormal rises
in the former, and timing of activation of the latter.
lf any of the above conditions occurs, the output
of the circuit causes the relay (RLl) to go OFF,
thereby cutting the supply power (AC) to the fixing
heater and lamp regulator.
2. Mechanism
Whenthevoltageofthethermistorreachesabout
1.0 V because of a rise in the temperature of the
fixing roller, the output of the No. 1 comparator of
(2309 goes ‘0’.
The lamp regulator generates LIGHT=l (scan-
ning lamp ON signal) at all times as long as the
scanning lamp is ON.
The above conditions cause the No. 2 compara-
tor of Q309 to generate ‘1’. thereby charging the
capacitar (C333).
C333 becomes fully charged about 20 seconds
thereafter: and output ‘1’ of the No. 2 comparator is
sent to the negative (-) input side of the No. 3
comparator. As a result, the output of the No. 3
comparator of Q309 goes ‘0’.
The above conditions generate ACOFF=O,
thereby causing the relay (RLI) to go OFF.
The copier can be reset after activation of the
errordetection circuit by turning it OFF and then ON.
Q309
+
Error
detection circuit
(DC controller PCB)
15313-g
1 1
/_
15303-6
Figure 3-45
COPYAIGHT 0 1992 CANON INC.
CANON NPZl2O/ZMO RN.0 MNY 1990 PRINTED IN JNPAN IIMPAIME RU JAPONI
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